A previously healthy woman had a febrile illness resembling aseptic meningoencephalitis. With the exception of mild increase in both CSF pressure and protein concentration, initial findings were normal, including negative bacterial cultures. Bilateral pyramidal and cerebellar signs with multiple lower cranial nerve pareses developed over a 48-hour period beginning on the tenth hospital day. Repeated blood and CSF studies had previously been nondiagnostic, but at that time, cultures became positive for Listeria monocytogenes. No underlying systemic disease or immunodeficiency was discovered. With appropriate antibiotic and supportive therapy, she made slow but significant improvement and, by the time of discharge from the hospital, had only minimal residual neurologic deficit. Clinical aspects of CNS listeriosis including the rare pontomedullary involvement are discussed.